A rotary die cutter includes a rotatable anvil roll which cooperates with a rotatable knife shaft assembly. The knife shaft assembly has an outer circumference with at least one die cutter associated therewith. The knife shaft assembly cooperates with the anvil roll to form a nip through which a web of material can pass. As a web of material passes between the nip, the die cutter will cut the material into a predetermined shape.
Since the nip between the anvil roll and the knife shaft assembly is very small, it is necessary that the anvil roll and the knife shaft assembly be manufactured to very close tolerances. Because of the close tolerances, most rotary die cutters utilize a solid die shaft having the die cutters integrally formed thereon. When replaceable die cutting inserts have been mounted onto the circumference of a rotatable die shaft, it has been found that it becomes difficult to maintain the required close tolerances. In addition, it is difficult to attach the die cutting inserts without also introducing additional forces which can cause the inserts to flex under load. Up until now, in order to assure that the nip dimension remains constant, it was necessary to regrind the die cutting inserts after they were mounted on the knife shaft assembly to assure that the correct nip dimension would be present. This was particularly necessary when two or more die cutting inserts were mounted about the outer periphery of a die shaft.
Rotary die cutters are used in many different industries to cut many different types of material. For example, rotary die cutters can be employed to cut paper, cardboard, plastic, laminates formed of two or more layers, absorbent materials such as wood pulp fluff, webs formed from natural or synthetic fibers, cellulose fluff, tissue, cotton, rayon and various other types of woven and nonwoven materials. Rotary die cutters are particularly useful in cutting a plurality of layers of different material which have been assembled to form an absorbent article such as a sanitary napkin or a pantiliner. Such products are normally constructed, from top to bottom, of a liquid-permeable cover sheet, one or more absorbent layers, a liquid-impermeable baffle, a layer of garment attachment adhesive and a removable peel strip. The various layers are normally bonded together by a construction adhesive and the article usually has a total thickness of between about 0.1 (2.5 mm) inches to about 1.0 inch (25.4 mm).
Now a replaceable and/or interchangeable die cutting insert for a rotary die cutter has been invented along with the die itself. Each replaceable and/or interchangeable die cutting insert has a unique configuration and includes mounting means for properly securing it to the outer circumference of a knife shaft assembly.